The invention relates to an apparatus for precisely indexing the orientation of a portion of a device with respect to a rigid structure of the device.
The invention relates more particularly to the use of such a device for re-establishing the faceting angle on a stone being ground in a faceting machine or in any other application wherein the relative orientation between two parts of a device must be repeatedly re-established. Such other uses are intended to include, but not be restricted to such uses as in a surveying transit.
Although the apparatus will be discussed with special emphasis on its use in a faceting machine, as noted above, it is not intended to so restrict its application.
In particular, in order to appreciate fully the inventive advance of the present invention over the prior art systems, consideration is to be given to a number of related devices which are of interest. In this respect, reference is made to U.S. Pat. No. 3,098,327, to Malin, which discloses a grinding and polishing machine for precious or semi-precious stones wherein the relative angle between a reference and a head-portion of the machine is set on a segmental protractor plate by pivoting the head about an axis. Additionally, the reproducible orientation of the protractor segment relative to the support structure of the machine is insured by means of a mechanical stop comprising a slot which engages a projection or stud.
Another faceting device using a protractor and pivot for setting the relative angles between the faceting head and a reference arm is shown in the U.S. Pat. No. 2,724,220 to Shaw. Although a relatively crude device, the arrangement used by Shaw shows the basic method which has normally been employed to set the relative angle between the faceting head and any reference arm. The device shown in the U.S. Pat. No. 3,940,888 to Wain is almost identical to the device of Shaw, in this respect.
Another patent of interest is U.S. Pat. No. 3,102,343 to Plank, showing a measuring apparatus for machine tools wherein a scanning portion of the device may be rotated about a test piece while the indicating mechanism remains stationary for easy reading. A multiple lever system is used to transmit motions of the scanning probe which deviate from a circle. The device according to Plank does not contemplate nor provide for precisely indexing the orientation of two portions of a device with respect to each other. Deviation from a circular norm rather than reproducibility of a preset angular orientation, appears to be the function of the Plank Device.
Another patent of interest is the U.S. Pat. No. 3,507,047 to Staedele for a nil gauging device for machine tools, in particular for setting-up work on milling machines, drilling machines or the like. The nil gauging device is intended for use in aligning the central axis of a drill chuck with a reference mandrel and with the edge of a work piece to determine a zero position. The deviation from the aligned position is transmitted to the pointer of a gauge by means of a dual lever mechanism. The eccentricity of the drill chuck or similar device is determined by rotating the drill chuck while the nil gauging device according to Staedele is in contact with the edge of the work piece and can be corrected for by relative adjustment of the work piece to the device. No means is provided in the Staedele reference teachings for locking together, at a pre-determined angle, different portions of a device, and thereafter indexing the orientation of these portions of the device with respect to a support structure of the device.
A further patent which is of interest is U.S. Pat. No. 3,811,229 to Montgomery, showing a gem faceter. This patent, similar to the Mailin patent and the Shaw patent, discussed above, sets the angle between the faceter head and a reference protractor by rotating the head or dop about a shaft until a pointer indicates the desired cutting angle on a protractor. To monitor the position of the support member or the cutting head, as an indication of when the grinding is completed, a sensor is mounted on a stop to provide a signal which is translated by an electrical circuit to a visual indication of the relative position of the support arm and the sensor. No levers or other mechanical means appear to be provided to amplify the relative movement between these devices. In fact, as the faceting head is mounted at a point further from the pivot means than is the electrical sensing device, the deviation of the head supported by the lever will be attenuated with respect to the electrical sensor.